i652 THE SUBDIVISIONS OF THE VEGETABLE KINGDOM. Sphceropleacece.—Sphairoplea annuUna is a curious Alga which appears occa¬sionally on flooded flelds or in other situations. Its thallus consists of simplethreads of cells which are of very various length, sometimes enormously long. Theside walls are thin, but the transverse walls are often thick, and both are liable tohave curious thick and quite irregular projections of cellulose. The chromatophoresform irregular rings at intervals, and contain many pjn-enoids. There are manynuclei, and several variable vacuoles in each cell. AU the cells may produce sexualorgans, the threads being either moncBcious or dicecious. The contents of the ceUswhich become antheridia become yellow-red, and break up to form a great numberof elongated, pointed spermatozoids. These escape through small holes in the waU.In the oogonia the protoplasm divides to form one or two series of sphericaloospheres, each with a colourless spot. The oospore has three membranes, of whichthe outermost is folded so as to give the oospore a star-like appearance. In germination the oospore produces 1-8 zoospores, which have a green posteriorand a pale-red anterior end. Each eventually stretches itself to form a spindle-shaped cell, and a multiplication of nuclei and pyrenoids takes place before trans¬verse divisions occur and a new SphceropleaSlavaent is produced. Parthenogenesisoccurs, but apparently no zoospores are formed other than those produced in thegermination of the oospore. ChcetophoracecB.—This family contains forms with a branching thallus, thebranches often ending in fine hairs. The chromatophore is parietal, with one ormore pyrenoids. Zoospores with two or four, and gametes with two flagella areproduced. Stigeoclonium, Braparnaldia, and Chcetophora ave three genera common in fresh¬water in this country, and all very sUmy to the touch. In the first-named genus thethallus is fixed by means of a basal disc of cells, the sole; the branching is simpleand irregular, the branches often ending in long multicellular hairs. Braparnaldiashows a marked distinction between axis and appendages. The axial ceUs aremuch larger, and at the same time poorer in chlorophyll than those of the branches.The branches come off in bunches, and often end in many-celled hairs. The chro¬matophore possesses many pyrenoids varying in number according to the size ofthe ceU. Chcetophora possesses a thaUus whose threads radiate and branch in aUdirections. The whole is surrounded by a mucUaginous investment of considerablefirmness, sometimes almost leathery in consistence, so that a ChcBtophora-'plant hasthe appearance of a slimy green ball. There are several other genera belonging to this family, many of them beingepiphytic or endophytic. Entoderma Uves in the cell-membranes of the BrownSea-weed Ectocarpus. Trentepohliacece.—This family differs from the last in possessing no hairs, and informing its zoospores in special zoosporangia. Trentepohlia is a fairly large genus containing forms mostly living in the airon damp stones and similar situations. The thallus consists of rounded thick-waUedcells, and is dichotomously or irregularly branched, partly creeping, partly upright.